The standard testing of hearing aids involves the evaluation of the hearing aid performance over a specified range of sound frequencies and sound levels. The current drain under such conditions of operation is also of significant interest in testing but to test for such requires the use of a battery substitute for supplying power to the hearing aid for measuring the instrument's current drain since the hearing aid current drain cannot be measured with a button battery installed therein. For hearing aids which incorporate a small button battery, such as is used in hearing aids which are ear worn, the connecting cable for delivering electrical power from the substitute power source must be flexible, adapted for good electrical coupling by making firm conductor contact with the electrical terminals of the hearing aid and be able to withstand the strains associated with repeated usage and flexing.
A battery substitute cable now in wide use utilizes flexible strips of sheet-like conductor material in a laminar arrangement with an insulator therebetween. The cable is provided at one end with an adapter of circular cylinder configuration which is sized to fit into the battery compartment of the hearing aid and has two electrical contact elements which engage the terminals of the hearing aid when it is placed in the battery compartment, and the battery compartment is closed by a hinged door, usually arcuate in shape, but having a transverse width dimension which corresponds to the axial thickness of the button battery. The electrical connection of the adapter to the cable conductors is a pressure clamp connection wherein each of the cable conductors is subjected to two ninety degree bends. As a result, this type of a battery substitute cable is characteristically fragile and tends to break or "short out" after a relatively short lifetime of usage.